A three-dimensional extension of a word originally describing two-dimensional shapes. Astronomical sense is in reference to the hollow spheres that carried the planets and stars in the Ptolemaic system. As a verb from c.1600. Orb weaver spider is first recorded 1889.

orb

emblem of royal power, usually made of precious metal and jewels and consisting of a sphere surmounted by a cross. The ball as a symbol of the cosmos, or of the universe as a harmonious whole, is derived from the ancient Romans, who associated it with Jupiter and, hence, with the emperor as his earthly representative.